One of the most popular biological assays used internationally to assess the chronic toxicity of chemical compounds and to monitor effluent discharges is the Daphnia reproduction test, particularly Daphnia magna, Daphnia pulex and Daphnia similis, but also with Ceriodaphnia. Some tests also use the count of fish eggs as evaluation criteria.
Currently the offspring counting of these organisms is made “naked eye” and backlit by technicians that count and pick every single organism, one by one, from the medium. This process must be repeated for the different treatments—for example different concentrations of chemical compound or effluent—and the various replications of each treatment. Thus, this procedure takes a lot of time and it is under the possibility of human error, and it represents a health risk to the technician, as it requires a high eye effort and exposure due to contact or inhalation of contaminants present in the assay medium.
The chromatic characterization is rarely used in ecotoxicology tests, either acute exposure or using offsprings, being considered a subjective measure and/or too time consuming. This characterization can be done with the naked eye, being performed simultaneously with the counting of organisms, making it subjective, time consuming and subject to human error. Alternatively, it can be achieved using photography of each organism, and visually comparing the intensity of pigment with a gray scale. However, this method is rather time consuming and is also subject to human error. It should be noted that the chromatic characterization may be a very sensitive response parameter from the organisms. For example, in breeding tests, Daphnia sp. exposed to different concentrations of a particular chemical compound can produce a similar number of offspring but exhibiting different color patterns. Similarly, for example in acute exposure tests, Daphnia sp. exposed to different concentrations of a particular chemical compound may be alive but have different chromatic patterns. The chromatic evaluation can also indicate different feed intake levels, for example in response to different levels of dissolved oxygen in water.
In addition, this device allows the intake assessment in organisms, including Daphnia sp. and Ceriodaphnia sp., exposed to chemical compounds or contaminated effluents. This evaluation is performed through the chromatic characterization of the medium in which these organisms are at two different time points.
These documents illustrate the technical problem to be solved by this solution.